Methods and apparatuses for producing magnetoresistive apparatuses

ABSTRACT

Methods and apparatuses for producing magnetoresistive apparatuses are provided. Here, structures are formed for defining regions of the same magnetization, magnets are magnetized, and structures are formed within the magnets of the regions, for example, in order to define magnetoresistive elements.

FIELD

The present application relates to methods and apparatuses for producingmagnetoresistive apparatuses (e.g., component parts or components) andcorrespondingly to the produced magnetoresistive apparatuses.

BACKGROUND

Magnetoresistive apparatuses use magnetoresistive effects, in which aresistance changes depending on a magnetic field. Examples of suchmagnetoresistive effects are giant magnetoresistance (GMR), tunnelingmagnetoresistance (TMR), anisotropic magnetoresistance (AMR) or colossalmagnetoresistance (CMR). Bracketed together, these effects are alsoreferred to as xMR. Therefore, magnetoresistive apparatuses may be used,in general, for measuring magnetic fields.

By way of example, such magnetoresistive apparatuses are used in speed,angle or rotational speed measuring apparatuses, in which magnets aremoved relative to a magnetoresistive apparatus and hence the magneticfield at the location of the magnetoresistive apparatus changes in thecase of movement, which, in turn, leads to a measurable change inresistance. By way of example, for the purposes of an angle sensor, amagnet or a magnet arrangement may be applied to a rotatable shaft and amagnetoresistive apparatus may be arranged stationary in relationthereto.

Magnetoresistive sensor elements of such magnetoresistive apparatusestypically comprise a plurality of layers, of which at least one layer isa reference layer with a reference magnetization. In some applications,a magnetoresistive apparatus in the process comprises a plurality ofmagnetoresistive sensor elements, which have different referencemagnetizations. By way of example, such different referencemagnetizations may be achieved by means of a laser magnetization. Tothis end, a region to be magnetized is exposed to a magnetic fieldcorresponding to the desired magnetization, and a region to bemagnetized is then heated by means of a laser beam. In this case,examples of such applications, in which various reference magnetizationsare required, are angle sensors, compass sensors or specific types ofspeed sensors (for example, speed sensors in a bridge arrangementreferred to as monocells).

Particularly in the case of small structures, the resultingmagnetization in the case of laser magnetization is low when comparedwith a homogeneous magnetization process in a furnace; this is reflectedin lower signal levels of a correspondingly implemented magnetic fieldsensor. Here, the lower magnetization may be caused, for example, bydeflection of the laser beam at small structures, for example obliquestructure flanks and the like. Here, this problem increases withdecreasing structure dimensions, and so only insufficient magnetizationsmay be obtained for, in particular, small structure dimensions in sensorstructures. On the other hand, samples can only be magnetized completelyhomogeneously in such a furnace, and different reference magnetizationsin different regions on a substrate are not possible.

Therefore, it may be desirable to provide improved options for producingmagnetoresistive apparatuses which comprise sensor elements withdifferent reference magnetizations.

SUMMARY

A method as claimed in claim 1 and an apparatus as claimed in claim 14are provided. The dependent claims define further embodiments and amagnetoresistive apparatus produced by means of the method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating a method in accordance with one ormore embodiments;

FIG. 2 is a block diagram of an apparatus in accordance with one or moreembodiments;

FIGS. 3A-3B are schematic views of structures for exemplifying at leastpart of the method of FIG. 1 and the method of operation of theapparatus of FIG. 2;

FIGS. 4A-4B are schematic views of structures for exemplifying at leastpart of the method of FIG. 1 and the method of operation of theapparatus of FIG. 2;

FIGS. 5A-5B are schematic views of structures for exemplifying at leastpart of the method of FIG. 1 and the method of operation of theapparatus of FIG. 2;

FIGS. 6A-6B are schematic views of structures for exemplifying at leastpart of the method of FIG. 1 and the method of operation of theapparatus of FIG. 2;

FIG. 7 is a schematic illustration for exemplifying a lasermagnetization;

FIGS. 8A-8B are schematic views of structures for exemplifying at leastpart of the method of FIG. 1 and the method of operation of theapparatus of FIG. 2; and

FIGS. 9A-9B are schematic views of structures for exemplifying at leastpart of the method of FIG. 1 and the method of operation of theapparatus of FIG. 2.

DETAILED DESCRIPTION

Various embodiments are explained in detail below. These embodimentsonly serve for exemplification purposes and should not be construed asbeing restrictive. By way of example, a description of an embodimentwith a multiplicity of components, features or details should not beconstrued to the effect that all of these components, features ordetails are necessary for implementation purposes. Rather, suchfeatures, components or details may be replaced in other embodiments byalternative features, components or details, or they may also beomitted.

Moreover, further features or components, for example features orcomponents used conventionally for producing magnetoresistiveapparatuses (xMR apparatuses), may also be present in addition to theexplicitly described features or components of the example embodiments.

FIG. 1 depicts a method in accordance with an embodiment in the form ofa flowchart. The method of FIG. 1 may be implemented as part of aproduction process for producing magnetoresistive apparatuses. Here,further procedures or processing steps may be carried out before andafter the procedures described in detail below, for example proceduresand processes conventionally used for producing such apparatuses. Inparticular, the explicitly illustrated steps in this case relate to themagnetization, for example of a reference layer, in xMR structures. Byway of example, semiconductor components may be formed in asemiconductor wafer and contacted by metal layers before the depictedsteps, and xMR components may then be formed as further layers in suchprocessing. After the illustrated steps, it is possible to carry outsteps such as installation into a housing, electrical contacting bymeans of bond wires and the like. In other words, FIG. 1 is used toexplain those processing procedures, in particular, which distinguishthe example embodiment in FIG. 1 from conventional production methodsfor magnetoresistive apparatuses.

The method of the FIG. 1 starts with a substrate, for example asemiconductor wafer, on which one or more layers were deposited forforming magnetoresistive structures. By way of example, three layers maybe deposited for forming TMR structures, a first layer serving as areference layer, a second layer in which a resistance is subsequentlymeasured, and a third layer which serves as a free layer. In a TMRelement, the second layer is non-conductive and a current flow isproduced by a spin-dependent tunneling effect. The second layer iselectrically conductive in the case of GMR elements. Any materials whichare used for conventional magnetoresistive elements may be used asmaterials for such layers, in particular e.g. two layers offerromagnetic materials which are separated by a nonmagneticelectrically conductive layer. Other layer structures may also be usedin other xMR structures. Examples of materials for the first layer andthe third layer are ferromagnetic materials, such as e.g. Co, Fe, Ni,and alloys of these materials among themselves and with further elementssuch as e.g. B, N, Hf, O, or Si. The first layer may also haveadditional adjacent layers for e.g. improving the magnetic properties orthe structure, made of e.g. Ru, Cu or similar materials in order to forma synthetic antiferromagnet in combination with a further ferromagneticlayer, or/and a natural antiferromagnet (e.g. PtMn, IrMn, NiMn, FeMn, orthe like) for the purposes of stabilizing the magnetization. MgO,aluminum oxide, hafnium oxide are examples of materials for the secondlayer in TMR layer stacks. Cu, Cr and Ag are examples of materials forthe second layer in GMR layer stacks.

At 10, structures are formed on the substrate, said structures definingregions which are intended to obtain the same magnetization of e.g. areference layer. These structures may, in particular, be relativelylarge, for example have smallest dimensions in one direction of greaterthan 10 μm, greater than 20 μm, greater than 50 μm, or greater than 100μm. In particular, the structures separate various such regions from oneanother such that said regions do not influence one another during asubsequent magnetization step. To this end, use may be made, inparticular, of trenches through the aforementioned layers, said trenchesdefining the regions.

At 11, the regions defined thus are magnetized, for example by means oflaser magnetization, wherein different regions may obtain differentmagnetizations, but the magnetization within each region issubstantially homogeneous. Since the structures which define the regionsare relatively large, it is possible to achieve a high magnetization ofthe regions; in later example embodiments, this leads to acorrespondingly high capability, for example comparatively high signals,of the resultant apparatus.

At 12, structures are then formed within the regions in order to formindividual magnetoresistive elements, for example individual sensorelements. These structures may be substantially smaller than thestructures formed at 10, for example having dimensions of less than 5μm, less than 1 μm, or even smaller, with larger dimensions also beingpossible. Since the magnetization already took place (at 11), such smallstructure dimensions do not adversely affect the magnetization, incontrast to conventional procedures, in which small structures aremagnetized, e.g. by means of laser magnetization or by means ofspatially restricted magnetic fields.

FIG. 2 depicts a block diagram of an apparatus in accordance with anembodiment, by means of which the method of FIG. 1 may be implemented.Here, FIG. 2 shows a first structuring apparatus 20, a magnetizationapparatus 21, and a second structuring apparatus 22. A substrate to beprocessed passes through these apparatuses in order. As also alreadyexplained for the method of FIG. 1, further apparatuses may be disposedupstream and/or downstream of the illustrated apparatuses for thepurposes of carrying out further processing steps.

Here, in accordance with the explanations in relation to 10 in FIG. 1,the first structuring apparatus is configured to form structures fordefining regions in substrates, which regions are intended to obtain thesame magnetization. To this end, the first structuring apparatus maycomprise conventional apparatuses, e.g. etching apparatuses, lithographyapparatuses (e.g. photolithography or electron beam lithography,depending on structure dimensions), e.g. lithography apparatuses whichmake use of masks, depositing apparatuses for depositing layers, and thelike.

Substrates structured thus, e.g. semiconductor wafers, are then suppliedto the magnetization apparatus 21 for magnetizing the regions. Here, inparticular, the magnetization apparatus 21 may comprise a lasermagnetization apparatus. Then, the substrate with the regions magnetizedthus is supplied to the second structuring apparatus 22 for the purposesof forming relatively small structures within the regions in order todefine magnetoresistive elements, e.g. sensor elements. Similar to thefirst structuring apparatus 20, the second structuring apparatus 22 mayalso comprise conventional elements such as the photolithographyapparatuses, depositing apparatuses, etching apparatuses and the like,wherein these may be designed for smaller structures than thecorresponding apparatuses of the first structuring apparatus. However,the first structuring apparatus 20 and the second structuring apparatus22 may also use common apparatuses, devices and the like, for examplelithography apparatuses or etching apparatuses, wherein differentstructures are formed. The illustration as two blocks 20, 22 shouldtherefore be understood to be a functional illustration and this doesnot necessarily mean a spatial separation.

For the purposes of more detailed explanations in respect of the methodin FIG. 1 and the apparatus in FIG. 2, explanations are now provided onthe basis of schematically illustrated example structures, withreference being made to FIGS. 3A-B, 4A-B, 5A-B, 6A-B, 7, 8A-B and 9A-B.Here, FIGS. 3A-B, 4A-B, 5A-B, 6A-B, 8A-B and 9A-B, which may be referredto as FIGS. 3-6, 8 and 9, respectively, each show a plan view (theFigure denoted by “A” in each case) and a cross-sectional view (denotedby “B” in each case) of the structures in various states of processing,for example, by means of the method illustrated in FIG. 1 or theapparatus shown in FIG. 2. These structures merely serve forexemplification, and the precise type or form of the structures maydiffer, depending on the magnetoresistive apparatus to be produced.

FIGS. 3A and 3B show an example for an initial state before depositingor otherwise forming magnetic layers for forming magnetoresistiveelements in accordance with one or more embodiments. In thecross-sectional view of FIG. 3B, it is possible to see the uppermost twolayers of a substrate which has already been processed here. Referencesign 30 is used to denote a metal layer which, for example, serves toconnect and contact structures lying therebelow (said structures notbeing illustrated but only being indicated by dots), said structuresforming electronic components, and to connect the latter with themagnetoresistive elements discussed in the following. In otherembodiments, the metal layer 30 may also be deposited directly on a rawsubstrate. By way of example, a silicon wafer or any other semiconductorwafer may serve as a substrate, in which, as mentioned above, componentsmay, but need not, have been formed.

Reference sign 31 denotes a dielectric layer, for example made ofsilicon dioxide or silicon nitrite. As may also be identified in theplan view of FIG. 3A, the dielectric layer 31 has vias (“verticalinterconnect accesses”) 32 at various points. By means of the vias 32,which may consist of a metal or any other electrically conductivematerial, magnetoresistive structures formed in the following areelectrically connected to the metal layer 30 (and hence, optionally, tocomponents formed in a substrate). In other embodiments, the vias 32 andthe metal layer 30 may also be omitted, and a metal layer or otherelectrical contacting may be provided above the layers described belowfor the purposes of forming xMR elements. Even though a single metallayer 30 has been depicted, a plurality of metal layers may also beprovided, as is conventional, for example, when producing semiconductorcomponents.

Next, magnetic layers for forming xMR elements, for example TMRelements, are deposited on the layers depicted in FIGS. 3A and 3B. Thisis depicted in FIGS. 4A and 4B. In the example of FIGS. 4A and 4B, afirst magnetic layer 40, which subsequently serves as reference layer, aspacer layer 41, for example made of electrically conductive ornonconductive nonmagnetic material, and a third layer 43, which consistsof magnetic material and subsequently serves as a free layer formagnetoresistive elements, are deposited or formed in any other way.Depending on the magnetoresistive structures to be formed, it is alsopossible to deposit more than three layers or fewer than three layers.Examples of possible materials were already explained further above.

Next, as explained in relation to 10 in FIG. 1, structures for definingregions of the same magnetization are formed. To this end, a mask 50 isarranged on the arrangement of FIGS. 4A and 4B, wherein the mask may beformed by depositing material on the structure or positioned on thelayer stack (40-42) as a separate mask, for example as a hard mask orsoft mask. Gaps in the mask facilitate an etching of trenches 51. In theillustrated example, the trenches 51 surround a group of six vias (seeFIG. 3A) in each case and enclose regions which should subsequentlyobtain a magnetization which is the same within the region, with themagnetization being able to differ from region to region. In particular,the trenches 51 pass through the layer 40, which subsequently serve as areference layer.

Thus, the processes explained above develop structures which defineregions of the same magnetization. Here, the procedure explained abovemerely serves as an example, and other procedures are also possiblehere. By way of example, webs made of dielectric material may be formedat the locations of the trenches 51 of FIG. 5 on, e.g., the structure ofFIG. 3 in another embodiment. By way of example, this may be carried outby depositing a dielectric layer with subsequent structuring of same byway of conventional methods. Thereupon, the layers for forming themagnetoresistive elements (e.g. corresponding to layers 40-42 in FIG. 4)are deposited between the webs formed thus, for example by way of acorresponding mask or by depositing the layers and subsequently removingthe material deposited on the webs. Regions which are separated from oneanother (by way of the webs) are formed in this way.

Then, as shown in FIGS. 6A and 6B, a passivation 60, for example made ofsilicon dioxide or another dielectric material, may optionally beapplied to the layer stack 40-42 prior to the actual magnetization.

Next, magnetization of the regions 51 is carried out in accordance withreference sign 11 in FIG. 1. Here, in the depicted example, each of theregions 51 may obtain a different magnetization (i.e. a differentmagnetization direction) or different regions may obtain the samemagnetization, depending on the magnetoresistive elements to beproduced. Here, in particular, the magnetization may be brought about bymeans of a laser magnetization, as is illustrated schematically in FIG.7. In FIG. 7, regions of a substrate 72 to be magnetized (for example ofthe substrate with layers as indicated in FIGS. 6A and 6B providedthereon) are irradiated by a laser beam 71 emitted by a laser 70 in thepresence of a magnetic field produced by magnet 73, and hence saidregions are heated. The magnet 73 may be a permanent magnet, anelectromagnet or a combination thereof. Different magnetizations may beproduced in different regions by changing the alignment of the magnet 73from region to region. As a result of the regions being separated by thetrenches 51, a magnetization of one region does not have a substantialeffect on another region, and so the regions may be magnetizedseparately from one another. However, other magnetization methods mayalso be carried out, e.g. a magnetization by means of spatially tightlyrestricted magnetic fields and heating of the entire substrate.

Second structuring (as explained with reference to 12 in FIG. 1), whichis illustrated in FIGS. 8 and 9 as an example, occurs after the lasermagnetization. The structuring of FIG. 8 uses a mask 80 (for example, inturn, a hard mask) in order to remove parts of the layer 42, for exampleby etching. As a result of this, individual regions of themagnetoresistive layer 42 are removed. In FIG. 9, there is a furtherstructuring step, in which the layers 40 and 41 are also separated and apassivation layer 90 is deposited, as illustrated. To this end, it ispossible, once again, to use masks, etching processes or otherconventional lithography steps. As is possible to identify, thestructures formed in FIGS. 8 and 9 are smaller than the regions whichare defined in FIG. 5B. Since the magnetization already occurred on thebasis of the larger regions, the small structure dimensions, which areworked out in the FIGS. 8 and 9, do not have a disadvantageous effect onthe magnetization.

Illustrated structures (FIGS. 3-6, 8, 9) should be understood merely asexample. In particular, other forms of structures may also be formed inaddition to rectangular structures, the forms and dimensions of thestructures may deviate from what is illustrated, and additionalstructures such as adjustment marks, etc. may be present. As alreadyexplained above, the depicted structures merely serve for an improvedunderstanding of the method.

It is therefore possible, in the manner illustrated above, to producexMR apparatuses with small structures and a good magnetization, withmutually independent magnetizations in various regions. The preciseprocedure may differ, depending on the type of xMR apparatus to beproduced. Further structuring steps may also follow. By way of example,when producing a TMR angle sensor with four different magnetizationdirections in a reference layer, it is possible to carry out thestructuring of the regions (step 10) first, followed by a lasermagnetization (step 11 in FIG. 1) and then a structuring of an upperelectrode, followed by a structuring of a lower electrode (both e.g. instep 12 of FIG. 1).

A similar procedure may be carried out in the case of the TMR anglesensor with more than four different magnetization directions, which maybe helpful, for example, for canceling higher harmonics contributions(harmonic waves) during the measurement.

In the case of an xMR (e.g. TMR or GMR) angle sensor with four differentmagnetization directions, there may likewise initially be structuring ofthe regions (step 10), followed by a laser magnetization (11), withthese then being able to be followed by a structuring of the xMR (e.g.TMR or GMR) layer stack.

An xMR (e.g. GMR or TMR) speed sensor may also be produced in a similarfashion, said xMR speed sensor using differently magnetized xMRresistors in order to develop a sensor bridge which is less sensitive toinclinations. In principle, the illustrated techniques may be used, ingeneral, if locally different magnetizations should be produced, inparticular if small structure dimensions are required.

Here, the aforementioned exemplary embodiments should only be consideredto be non-restrictive examples.

The description and drawings merely illustrate the principles of thedisclosure. It will thus be appreciated that those skilled in the artwill be able to devise various arrangements that, although notexplicitly described or shown herein, embody the principles of thedisclosure and are included within its spirit and scope. Furthermore,all examples recited herein are principally intended expressly to beonly for pedagogical purposes to aid the reader in understanding theprinciples of the disclosure and the concepts contributed by theinventor(s) to furthering the art, and are to be construed as beingwithout limitation to such specifically recited examples and conditions.Moreover, all statements herein reciting principles, aspects, andembodiments of the disclosure, as well as specific examples thereof, areintended to encompass equivalents thereof.

Furthermore, the following claims are hereby incorporated into thedetailed description, where each claim may stand on its own as aseparate example embodiment. While each claim may stand on its own as aseparate example embodiment, it is to be noted that—although a dependentclaim may refer in the claims to a specific combination with one or moreother claims—other example embodiments may also include a combination ofthe dependent claim with the subject matter of each other dependent orindependent claim. Such combinations are proposed herein unless it isstated that a specific combination is not intended. Furthermore, it isintended to include also features of a claim to any other independentclaim even if this claim is not directly made dependent to theindependent claim.

It is further to be noted that methods disclosed in the specification orin the claims may be implemented by a device having means for performingeach of the respective acts of these methods.

Further, it is to be understood that the disclosure of multiple acts orfunctions disclosed in the specification or claims may not be construedas to be within the specific order. Therefore, the disclosure ofmultiple acts or functions will not limit these to a particular orderunless such acts or functions are not interchangeable for technicalreasons. Furthermore, in some embodiments a single act may include ormay be broken into multiple sub acts. Such sub acts may be included andpart of the disclosure of this single act unless explicitly excluded.

What is claimed is:
 1. A method for producing a magnetoresistiveapparatus, comprising: structuring a substrate with defined regions,magnetizing at least one layer of the defined regions with amagnetization which is the same within each defined region of thedefined regions, and forming structures within the defined regions. 2.The method as in claim 1, wherein forming the structures within thedefined regions comprises forming magnetoresistive elements.
 3. Themethod as in claim 1, wherein the structures formed within the definedregions have a smallest dimension of less than 5 μm.
 4. The method as inclaim 1, wherein the defined regions have a smallest dimension ofgreater than 10 μm.
 5. The method as in claim 1, further comprising:forming a magnetoresistive layer stack, and wherein structuring thesubstrate with the defined regions comprises structuring of themagnetoresistive layer stack.
 6. The method as in claim 5, wherein thestructuring of the magnetoresistive layer stack comprises formingtrenches in the magnetoresistive layer stack to define the definedregions.
 7. The method as in claim 1, wherein structuring the substratewith the defined regions comprises forming dielectric webs forrestricting the defined regions, and wherein the method furthercomprises forming magnetoresistive layer stacks in the defined regions.8. The method as in claim 1, wherein magnetizing the at least one layerof the defined regions comprises magnetizing at least two of the definedregions with mutually different magnetizations.
 9. The method as inclaim 1, wherein magnetizing the at least one layer of the definedregions comprises magnetizing a reference layer.
 10. The method as inclaim 1, further comprising: depositing a dielectric layer afterstructuring the substrate with defined regions and prior to magnetizingthe at least one layer of the defined regions.
 11. The method as inclaim 1, wherein forming the structures within the defined regionscomprises structuring magnetoresistive layer stacks.
 12. The method asin claim 1, wherein forming the structures within the defined regionscomprises structuring electrodes for magnetoresistive elements.
 13. Themethod as claim 1, wherein magnetizing comprises laser magnetizing. 14.An apparatus for producing a magnetoresistive apparatus, comprising: afirst structuring apparatus configured to define regions in a substrate,a magnetizing apparatus for magnetizing at least one layer within theregions, and a second structuring apparatus for forming structureswithin the regions.
 15. The apparatus as in claim 14, wherein themagnetizing apparatus comprises a laser magnetizing apparatus.
 16. Theapparatus as in claim 14, wherein at least one of the first structuringapparatus or the second structuring apparatus comprises at least one ofa lithography device, a material depositing device or an etching device.17. The apparatus as in claim 14, wherein the first structuringapparatus and the second structuring apparatus comprise at least onecommon device.
 18. A magnetoresistive apparatus produced by a method,the method comprising: structuring a substrate with defined regions,magnetizing at least one layer of the defined regions with amagnetization which is the same within each defined region of thedefined regions, and forming structures within the defined regions. 19.The apparatus as in claim 18, wherein the magnetoresistive apparatuscomprises at least one of a giant magnetoresistance (GMR) apparatus, atunneling magnetoresistance (TMR) apparatus, an anisotropicmagnetoresistance (AMR) apparatus or a colossal magnetoresistance (CMR)apparatus.
 20. The apparatus as in claim 18, wherein the structures aremagnetoresistive elements.